D. Viehland

Direct observation of the near-surface layer in Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} using neutron diffraction

Spatially resolved neutron diffraction as a function of crystal depth in Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} reveals the presence of a distinct near-surface region where a strong distortion in the lattice exists. A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale {approx}100 {mu}m. This confirms a previous assertion, based on a comparison between high-energy x rays and neutrons, that such a near surface region exists in the relaxors. Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed.

Crafting the strain state in epitaxial thin films: A case study of CoFe 2 O 4 films on Pb ( Mg , Nb ) O 3 − PbTiO 3

The strain dependence of electric and magnetic properties has been widely investigated, both from a fundamental science perspective and an applications point of view. Electromechanical coupling through field-induced polarization rotation (PRO) and polarization reorientation (PRE) in piezoelectric single crystals can provide an effective strain in film/substrate epitaxial heterostructures. However, the specific pathway of PRO and PRE is a complex thermodynamic process, depending on chemical composition, temperature, electric field and mechanical load. Here, systematic studies of the temperature-dependent field-induced phase transitions in Pb(Mg,Nb)O3-PbTiO3 single crystals with different initial phase and orientation configurations have been performed. Different types of strains, volatile/nonvolatile and biaxial/uniaxial, have been measured by both macroscopic and in-situ X-ray diffraction techniques. In addition, the strain state of epitaxial Mn-doped CoFe2O4 thin films was examined by magnetic anisotropy measurements, where a giant magnetoelectric coupling has been demonstrated.

Intermediate ferroelectric orthorhombic and monoclinicMBphases in [110] electric-field-cooledPb(Mg1∕3Nb2∕3)O3–30%PbTiO3crystals

Office of Naval Research under Grant Nos. N000140210340, N000140210126, MURI N0000140110761